高分子水溶液の微小円柱まわりの流れ中における流動複屈折分布(<小特集>非ニュートン性,機能性を示す複雑流体の流動と応用)

概要

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Flow-induced birefringence distribution and velocity field were measured in a slit flow containing a tiny cylinder, which was 550μm in diameter and 200μm in height. Xanthan gum solution, which has a non-Newtonian property owing to network structure in the liquid, was used for a test fluid. The laser beam was collected, resulting beam diameter was 6μm, and the birefringence distribution was measured around the tiny cylinder in every 100μm step in space. Consequently, in the upstream region of the cylinder, birefringence became small as the fluid particle approached the cylinder. This is because the flow is decelerating upstream of the cylinder and the fluid particle is elongated in the direction perpendicular to the flow. Furthermore, just upstream of the cylinder the birefringence became large and the molecular orientation was aligned in the direction perpendicular to the flow. On the other hand, downstream of the cylinder the flow is accelerating, thus the fluid particle is elongated in the flow direction. As a result, the birefringence becomes large on the centerline behind the cylinder. This result shows that the strain of the fluid particle generated by flow behind the cylinder is not disappeared even at the fully downstream region.
2009-05-25